Effects of satiation and starvation on nematocyst discharge, prey killing, and ingestion in two species of sea anemone.

Studies spanning 60 years with several cnidarian species show that satiation inhibits prey capture and ingestion and that starvation increases prey capture and ingestion. Most have attributed the effects of satiation to inhibition of nematocyst discharge. We hypothesized that satiation inhibits prey capture and ingestion in sea anemones (Haliplanella luciae and Aiptasia pallida) primarily by inhibiting the intrinsic adherence (i.e., holding power) of discharging nematocysts. Using a quantitative feeding assay for H. luciae, we found that satiation completely uncoupled prey killing from prey ingestion, while nematocyst-mediated prey killing was only partially inhibited. Using A. pallida to measure nematocyst discharge and nematocyst-mediated adhesive force, we showed that satiation completely inhibited the intrinsic adherence of discharging nematocysts from Type B and Type C cnidocyte/supporting cell complexes (CSCCs), while only partially inhibiting nematocyst discharge from Type Bs. These inhibitory effects of satiation were gradually restored by starvation, reaching a maximum at 72 h after feeding. Thus, the effects of satiation and starvation on prey killing and ingestion in two species of acontiate sea anemones are primarily due to changes in the intrinsic adherence of nematocysts from both Type B and Type C CSCCs.